Introduction

Mechanical, metabolic, and septic complications are associated with PN therapy.
Mechanical and septic complications are related to obtaining and maintaining a
route of central vascular access. Metabolic complications require both a thorough
assessment of patients prior to initiation of PN and close monitoring while receiving
PN. Careful attention to detail minimizes complications.

Venous thrombosis is one of the two most common problems that occur after central venous
access is established. The other is infection. Venous thrombosis is associated with
significant morbidity rates. Signs include distended neck veins and swelling of the
face and ipsilateral arm. The risk of venous thrombosis is greater if patients are
dehydrated, have certain malignancies, have had prolonged bed rest, have venous stasis,
have sepsis, or have hypercoagulation. Additional risk factors include morbid obesity,
smoking, or ongoing estrogen therapy.

Infectious complications

PN imposes a chronic breech in the body's barrier system. The infusion apparatus from
container to catheter tip may prove a source for the introduction of bacterial or fungal
organisms. The operator inserting the venous catheter, the pharmacist compounding the
solution, or the care-giver hanging the bag or changing the site dressing may contaminate
the patient's "lifeline."

Infection is one of the two most common problems that arise after central venous access is
established. The other is venous thrombosis, discussed earlier. The mortality rate from catheter
sepsis may be as high as 15%.

The primary preventive measures include adhering to strict aseptic procedure while establishing
access and providing care of the dressing and line, and prohibiting the use of the TPN line for
other purposes. Other preventive measures include:

Changing the dressing routinely (every 48-72 hours) or when it becomes soiled, wet or loose.
The care-giver should wear a mask and gloves while changing the dressing.

Extending the application of antimicrobial solution at least 1 inch beyond the final dressing.

Placing a sterile sponge over the catheter, then placing an occlusive dressing.

Inspecting the site for tenderness, erythema, edema, loose sutures, or drainage.

Changing the TPN intravenous tubing every 48 hours. A 0.22-Ám in-line filter should be
used whenever fat is not being infused.

Avoiding violation of TPN catheters for central venous pressure monitoring or the
administration of intravenous medications or blood products.

Metabolic complications

Metabolic complications fall into two broad categories: early and late complications.
Those in the first category occur early in the process of feeding and may be anticipated.
They are avoided by careful monitoring and appropriate adjustment of intake. Late
metabolic complications are less predictable. They may be caused by an exacerbation of
preexisting abnormalities, unpredictable long-term requirements, inadequate solution
composition, or failure to monitor adequately.

Metabolic complications of PN

Early complications

Late complications

Volume overload

Essential fatty acid deficiency

Hyerglycemia

Trace mineral deficiency

Refeeding syndrome

Vitamin deficiency

Hypokalemia

Metabolic bone disease

Hypophosphatemia

Hepatic steatosis

Hypomagnesemia

Hepatic cholestasis

Hyperchloremic acidosis

Fluid and electrolyte complications

Electrolyte management is one of the most difficult aspects of PN therapy. Often electrolytes
are outside of the normal range based on an underlying cause rather than directly related to the
PN solution. For this reason, no specific guidance can be given to adjust individual electrolytes
based on laboratory serum concentration. Instead, incremental dose adjustments are made concurrent
with treatment of the underlying cause of electrolyte abnormality. Patient acuity will prescribe
the magnitude of dosing adjustments as well as the need for more frequent monitoring. In general,
supplemental electrolyte doses in response to an acute underlying condition are best managed
outside of PN therapy.

Refeeding syndrome

Refeeding of severely malnourished patients may result in "refeeding syndrome"
in which there are acute decreases in circulating levels of potassium, magnesium,
and phosphate. The sequelae of refeeding syndrome adversely affect nearly every
organ system and include cardiac dysrhythmias, heart failure, acute respiratory failure,
coma, paralysis, nephropathy, and liver dysfunction.

The primary cause of the metabolic response to refeeding is the shift from stored
body fat to carbohydrate as the primary fuel source. Serum insulin levels rise,
causing intracellular movement of electrolytes for use in metabolism.

The best advice when initiating nutritional support is to "start low and go slow".
Recommendations to reduce the risk of refeeding syndrome include: